During central nervous system (CNS) development, glial precursor proliferate in subventricular zones and then migrate throughout the CNS to adopt their final destinations and differentiate into various types of mature glial cells. Although several growth factors promoting the proliferation and/or differentiation of glial precursors have been identified, very little is known about the nature of signals that guide glial cell migration in the CNS. The in vitro migration responses of these CNS cells were studied in two different collaborative studies with Drs. Armstrong and Dubois-Dalcq (NINCDS) and Dr. Colton (Georgetown University Medical Center). In these studies, the microchemotaxis chamber assay was used to study whether polypeptide growth factors and/or extracellular matrix molecules may mediate the migration of two major glial cell types, type 1 astrocytes and oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells. Type 1 astrocytes migrated toward laminin and complement-derived C5a. In contrast, O-2A progenitors migrated toward platelet-derived growth factor (PDGF), which also functions as a mitogen for these cells. Using a new method to simultaneously assay migration and DNA synthesis, it was found that O-2A progenitors can migrate toward PDGF even when DNA replication is inhibited with an antimitotic agent. These results demonstrate that migration of different types of glial cells can be induced in vitro by specific signaling molecules, which are present in the developing brain and may stimulate migration of glial cells prior to CNS myelination. Two manuscripts were written as a result of this work. One manuscript with Dr. Colton is in press in the Journal of Neuroscience Research; the other manuscript with Drs. Armstrong and Dubois-Dalcq is submitted to the Journal of Neuroscience Research.